Physical Characteristics of Nanoparticles Emitted From Incense Smoke

Siao Wei See
Department of Chemical and Biomolecular Engineering, National University of Singapore

Rajasekhar Balasubramanian
Division of Environmental Science and Engineering, National University of Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore

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     Last modified: March 15, 2006

Abstract
Exposure to smoke from incense burning in indoor environments is of great health concern. Incense sticks are habitually burned in various religious settings ranging from the far Eastern temples to the Western Catholic churches, and also used in aromatherapy. Given the wide usage of incense sticks, it is important to characterize the emissions of airborne particulate matter from this indoor activity so as to assess its potential impact on human health and identify appropriate emission control strategies. However, there is a paucity of data in the literature on the physical characteristics of airborne particles in incense smoke, especially the number concentration of particles of different sizes. This information is needed for health risk assessment since particle counts are currently thought to be a better indicator of potential health effects rather than particle mass.

It is particularly important to characterize airborne nanoparticles (< 50 nm) in incense smoke because smaller particles can be more efficiently deposited deep in the lung, or translocated to other extrapulmonary organs upon inhalation. However, nanoparticles add very little to the total mass loading of aerosols even though their numbers may be much larger than larger particles, and can thus go unnoticed in the conventional gravimetric determination of airborne particulate matter. It is therefore imperative to investigate and document the size distribution as well as the number concentrations of airborne particulate matter in the nanometer range.

An intensive study was carried out to determine the number concentration and size distribution of airborne nanoparticles in incense smoke. Different types of common incense used by various religious groups were investigated in terms of emissions of airborne particles in the size range of 5.6 nm to 560 nm using the Fast Mobility Particle Sizer (FMPS, TSI Incorporated, MN, USA) with a particle size resolution of 16 channels per decade or 32 channels in total. The real-time data obtained on the emission of nanoparticles from various types of incense and at different stages of the burning process will be presented. In addition, the health implications of incense smoke will be discussed in the symposium.